Can you use Spline36Resize on just the width?

[VideoFanatic]

My video is 720 x 576. I'm trying to restore it to the correct proportions. I want to use Spline36Resize(540,576) BEFORE using QTGMC as it will make QTGMC quicker. Resizing the width is safe as you won't get interlacing artifacts but what about the height? I'm keeping the height the same size as it originally was so will I get interlacing artifacts?

Is there a way to use Spline36Resize by just telling it to only resize the width?

[pandy]

My video is 720 x 576. I'm trying to restore it to the correct proportions. I want to use Spline36Resize(540,576) BEFORE using QTGMC as it will make QTGMC quicker. Resizing the width is safe as you won't get interlacing artifacts but what about the height? I'm keeping the height the same size as it originally was so will I get interlacing artifacts?

Is there a way to use Spline36Resize by just telling it to only resize the width?

No risk - Resize is performed in 2 passes - once horizontal, second vertical or in opposite direction - http://avisynth.nl/index.php/Resize

Important: AviSynth has completely separate vertical and horizontal resizers. If input is the same as output on one axis, that resizer will be skipped. Which one is called first, is determined by which one has the smallest downscale ratio. This is done to preserve maximum quality, so the second resizer has the best possible picture to work with.

[themaster1]

spline36resize(540,576)
it's generally better to resize after because every resizing techniques introduce artefacts (strong aliasing with spline36resize)
As you're downsizing you may want to use bilinearresize instead but that's your choice

[VideoFanatic]

I didn't see any artifacts when downscaling 1920 x 1080 to 1280 x 1080. So I thought it would be OK to do the same with 720 x 576 to 540 x 576.

[Vidd]

I didn't see any artifacts when downscaling 1920 x 1080 to 1280 x 1080. So I thought it would be OK to do the same with 720 x 576 to 540 x 576.

You may not see artifacts, but what matters is if QTGMC sees artifacts. But it is your choice for quality vs speed.

[pandy]

So I thought it would be OK to do the same with 720 x 576 to 540 x 576.

Highly related to content nature... generally you should avoid loosing data before any important signal processing, in fact frequently data are oversampled to improve processing quality (codecs use subpixel motion estimation precision - as you know there no such thing like subpixel - subpixels are created due oversampling (usually 2 - 4 times already) - this is frequent source for "slow processing".

If you believe that quality is not sacrificed and you are happy with speed up then go for 540 - if not stay with 720.

[theewizard]

The question is
Is the aspect ratio currently correct at 720
How does the video look?
Are round objects ..round?
Then you don't want to compress the width
If things are stretched horizontally, out of proportion, the yes.. Resize the width to get the correct aspect ratio